The objectives of this project are to characterize the toxicity and carcinogenicity of 60 Hz sinusoidal magnetic fields in Fischer 344 rats and B6C3Fl mice, to determine if such fields alter pineal function, and to determine if such fields cause developmental or reproductive toxicity. Phase 1 comprises only those activities associated with procurement of equipment and materials needed to construct the exposure and monitoring systems, the construction/renovation of the exposure and monitoring systems, and the developmental effort needed to determine that the systems function appropriately and meet the specifications. Phase 2 involves the conduct of an 8-week study, developmental and reproductive toxicity studies, and a 104-week study in which animals are exposed to magnetic fields of specified intensities (4 exposure groups and an untreated control group) using the exposure system developed in Phase 1. The 8-week study includes clinical laboratory studies; determination of pineal melatonin and serotonin-N-acetyltransferase, and blood melatonin and its 6-OH metabolite; and a complete necropsy and histopathologic evaluation of test animals at the end of the study. The 104-week study includes complete necropsies and histopathologic evaluation at the end of the study.